1. Field of the Invention
The present invention relates to a method for producing a laminated base material composing a printed wiring board (printed board or printed circuit board) widely used in the electronic field.
2. Related Background Art
In commonly used conventional printed wiring boards of this type, a printed wiring board including a substrate which comprises an insulating layer and a conductor which is laminated on and forming a circuit pattern on the insulating layer, and a covering material laminated on the substrate for protecting the conductor. As the covering material, a base material of polyimide film having an adhesion layer of a thermoplastic resin such as thermoplastic polyimide on the back side is employed because of high heat resistance, practically high flow temperature, and no thermoplasticity (e.g., refer to Japanese Patent Application Laid-Open No. 62-85941).
However, the art disclosed in Patent Literature 1 causes increased transmission loss in electric signals under the influence of the adhesion layer (thermoplastic resin layer) described above to degrade electric characteristics of a printed wiring board in some instances, which requires improvement.
In view of these circumstances, it is a first object of the present invention to provide a laminated base material that can reduce transmission loss in electric signals and a method for producing the same, and it is a second object to provide a printed wiring board that can enhance electric characteristics.